The 2KLGA is a key intermediate in the synthesis of L-ascorbic acid. For industrial production, 2KLGA is chemically synthesized from D-sorbitol by oxidation according to the Reichstein's method. Meanwhile, many microorganisms inclusive of the microorganisms belonging to the genus Gluconobacter are known to convert D-sorbitol to 2KLGA through an enzymatic oxidation. The microorganisms belonging to the genus Gluconobacter have been improved by genetic engineering using conjugal transfer and transposon. However, because of the low production of 2KLGA by these microorganisms, they have not been utilized in the industrial production yet.
Accordingly, there has been a desire for a more efficient and simplified method for the production of 2KLGA.
It is also well known that, in secondary metabolite production by microorganisms such as that of 2KLGA, a mere insertion of a gene (group) responsible for the biosynthesis of a substance into a plasmid and culture of the cells of microorganism, which have been recombined with this plasmid, does not necessarily result in an improved production of the desired substance, but rather, may degrade the productivity Thomas, D. I. et al., J. Gen. Microbiol., 137, pp. 2331-2337 (1991)!.